Light Fields Caused by Quantum Diffusion

H. C. Fan, Liyun Hu

H. C. Fan, Liyun Hu

David Thomas Pegg

We examine the phase relationships between different packets of a beam of light emitted from a cavity through a partially transmitting mirror. We find that the beam has a pronounced phase coherence even when the intracavity field has a completely indeterminate phase such as, for example, when it is in a pure photon number state. In this case, the phase coherence can be directly attributed to entanglement caused by the partially transmitting mirror and, even though the external light has phase coherence, it has no identifiable phase. Consequently there is no phase diffusion but there is diffusion of the phase difference between a packet and the intracavity field. Remarkably, we find that the phase coherence of the beam is almost independent of the intracavity state, provided this has a reasonably narrow number-state distribution about a large mean value.

Yanpeng Zhang, Chenli Gan, Shahid Munir Farooqi +3 more

Four-level polarization beats (FLPBs) with broadband noisy light are investigated by use of chaotic field, phase-diffusion, and Gaussian-amplitude models. The polarization beat signal is shown to be particularly sensitive to the statistical properties of the Markovian stochastic light fields with arbitrary bandwidth. Different stochastic models of the laser field affect only the fourth-order coherence functions. The constant background of the beat signal originates from the amplitude fluctuation of the Markovian stochastic fields. The Gaussian-amplitude field shows fluctuations larger than the chaotic field, which in turn exhibits fluctuations much larger than for the phase-diffusion field with pure phase fluctuations caused by spontaneous emission. It is also found that the asymmetric behaviors of the polarization beat signals due to the unbalanced dispersion effects between the two arms of an interferometer and to the Doppler width do not affect the overall accuracy when FLPBs are used to measure the energy-level difference between two states that are dipolar forbidden from the ground state.

Antonín Luk¿, Vlasta Peřinová

S. W. Koch, Ewan M. Wright

Transverse beam-profile variations are investigated for a system which shows cavityless optical bistability due to increasing absorption. Coupled transport equations for the light field and the excitation density are derived and solved numerically for the case of an optically thin sample, where longitudinal density variations can be neglected and where diffusion of the excitation is the dominant transverse coupling mechanism. Assuming a Gaussian input beam, the increasing absorption is shown to cause substantial profile modifications when the medium undergoes the transition from low to high absorption. The formation of spatial ring structures is predicted and it is shown that transverse carrier diffusion plays an important role in determining both the steady-state and the temporal response of the system.